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1. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 2277
Compaction and seepage characteristics of Fly ash mixed with
Bentonite
Mayank Pandey1, Prof Rajesh Jain2
1ME Scholar, 2Associate Professor
Jabalpur Engineering College, Jabalpur (M.P.)
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The present study has been carried out to find out the compaction properties and seepage characteristics of fly ash and
bentonite mixtures. Laboratory tests were conducted at different proportions of fly ash and bentonite. Fly ash, a waste
generated by thermal power plants is as such a big environmental concern. The investigation reported in this paper is carried
out to study the utilization of fly ash in lining applications with bentonite additive so as to provide an environmentally
consistent way of its disposal and reuse. Fly ash is generated in tons as a residue from burning of coal in the power plants. The
components of fly ash vary according to the type of coal being burned. But mainly all fly ash include substantial amounts of
silicon dioxide (SiO2) (both amorphous and crystalline) and calcium oxide (CaO). Bentonite is clay formed as a result of
chemical weathering of volcanic ash. It consists of montmorillonite. Due to its swelling properties, bentonite provides as a self-
sealing, low permeability hydraulic barrier. Fly ash is cohesion less material and having very low compressive and shear
strength however its strength can be increased by adding low cost cohesive materials such as lime and clayey soil whereas
bentonite is clay having high swelling properties when it comes in contact with the water. Wastes are generated more and
more with increasing industrialisation and population growth. Based on the safety level, these wastes can be controlled by
different options such as waste reduction, separation and recycling, resources recovery through waste processing, waste
transformation, and environmentally sustainable disposal on land. The most frequently used disposal option for solid waste in
the landfill because of its low cost and efficiency. In the present study seepage and compaction characteristics of fly ash mixed
with bentonite are studied to enable its use in various engineering applications such as land fill liner and subgrade material of
pavements.
Keywords: Fly ash, Bentonite, lining applications, subgrade material
Introduction
Landfills are the most popular municipal solid waste disposal system. The design of liner is made so as to isolate the waste
from the environment minimizing the passage of leachate into the groundwater. To ensure this the important
characteristics for compacted landfill liners are selection of materials, hydraulic conductivity, strength, compressibility
and contaminant retention capacity. Fly ash is the notorious waste product of coal based electricity generating thermal
power plants, known for its ill effects on agricultural land, surface and sub-surface water pollution, soil and air pollution
and diseases to mankind. Researchers have proposed few ways of reusing fly ash for variety of application. Fly ash
particles are almost totally spherical in shape, allowing them to flow and blend freely in mixtures. With this in view, the
present study purports to examine the suitability of fly ash as a landfill liner material. The major objective of this study is
to maximize the use of fly ash for the liner application. Therefore, different fly ash-bentonite mixes were subjected to
hydraulic conductivity, Shear strength and compressibility evaluation. Mishra1 et al. (2010) worked on mixtures of
expansive soil such as bentonite with fly ash and pond ash can is used as compacted barriers. Lakshmikanth H2(2004)
worked on the Properties of Fly ash as Hydraulic Barrier, Soil and Sediment Contamination. Yilmaz3 (2001) was carried
out an investigation on the utilization of fly ash and bentonite mixture as a bottom and/or upper liner material at waste
disposal areas. In this study, Catalagziflyash was mixed with bentonite, as binding material, at 10, 20 and 30
percentages (dry weight bentonite/dry weight Catalagziflyash) to obtain less permeable liner material 1. Alam J4 et el.
(2012) also worked on the Seepage characteristics and geotechnical properties of fly ash mixed with bentonite. Bello5
(2013) worked on the basic attributes of a suitable liner. the presence of significant amount of a clay minerals and having a
hydraulic conductivity less than or equal to 1×10-7acm/s. Therefore, different fly ash-bentonite mixes were subjected to
different tests to determine its swelling properties.

2. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 2278
Materials used
Fly ash
The fly ash used in this present study is an industrial by-product obtained from the Sanjay Gandhi Thermal power plant
situated in Birsinghpur Tehsil in Umaria district of Madhya Pradesh. Fly ash used in this study is class F fly ash.
Bentonite
The bentonite used for the project work was Sodium bentonite which is naturally occurring hydrated aluminium silicate
clay. It exhibits extremely high swelling and water absorbency properties. Bentonite used in this study is sodium bentonite
purchased from the market of Jabalpur in Madhya Pradesh.
Methodology
All the tests were carried out as per the relevant Indian Standards for determining the compaction behaviour and swelling
properties of fly ash and bentonite mixture at various proportions varying from 4 % bentonite, 8% bentonite, 12%
bentonite and 20% bentonite with remaining fly ash content P.V.V.Satyanarayana6 et al. (2013) works on the red soil and
bentonite mixture and obtained that the mixture is best suited for lining purpose.
Compaction Characteristics
Heavy compaction test was carried out on specimens as per IS 2720 (Part VIII) 1980. The compaction curves for fly ash-
bentonite mixture was obtained and the OMC and MDD values are given in Table.
These OMC and MDD values obtained from laboratory compaction test provide a reference point while estimating the
actual water content of the field-compacted soil liner. The variation of MDD and OMC of the compacted fly ash-bentonite
mixtures are presented in the Figure.
S No. Bentonite content
(%)
Bentonite fly ash mixture
OMC MDD
1 0 39 1.125
2 4 36 1.143
3 8 34 1.16
4 12 32.5 1.19
5 20 30.5 1.27
Bentonite(%)
25
30
35
40
45
0 5 10 15 20 25
OMC
OMC(%)

3. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 2279
Fig. Variation of Optimum moisture content with bentonite
Bentonite(%)
Fig. Variation of maximum dry density with bentonite
Permeability Characteristics (IS: 2720- Part 17, 1986)
The permeability of pure fly ash and bentonite as well as of their mixes was measured by Falling Head Test method, after
their compaction at optimum moisture content, maximum dry density and by saturating it for three days.
Formula used: The coefficient of permeability has been determined by the relation.
K=[2.303 aL / (At)].Log10(h1/ h2)
K = Coefficient of permeability in cm/sec. at test temperature
a = Inside cross sectional area of stand pipe in cm2
A = Cross sectional area of soil sample
L = Length of soil sample in cm
h1 =Initial head in cm
h2= Final head in cm
t = Time interval in seconds in which the head drop from h1 to h2
S No. Bentonite
Content
Coefficient of Permeability of Bentonite Fly ash
Mixture(cm/sec)
1 0 148x10-7
2 4 130x10-7
3 8 115x10-7
4 12 17.9x10-7
5 20 .9x10-7
1.08
1.12
1.16
1.2
1.24
1.28
0 5 10 15 20 25
MDD
MDD(%)

4. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 2280
Conclusions
 With increase in the bentonite content, the maximum dry density (MDD) of the mixture is increased and the
optimum moisture content (OMC) is decreased.
 An increase in bentonite content of 12%-20% induced plasticity in the fly ash-bentonite mixture which led to
better bonding between particles upon compaction.
 The conclusion drawn from the present study is that 20% bentonite-fly ash mix is an optimum mix that can be
safely used as a subgrade material of pavements and as cover or liner at waste disposal sites, as per the design
criteria clays with permeability <1x10-7cm/sec is considered for landfill liner.
 Up to 8% bentonite, the permeability reduces at a constant rate of about 9 %, thereafter up to 20% bentonite, the
reduction in the value of permeability was observed to be about 7%. So a mixture of fly ash mixed with 20%
bentonite may be used as a low permeable mass.
References
1. Mishra A.K.,Ohtsuba M.,Li L.Y. and Higashi T,(2010),”Influence of the bentonite on the consolidation behaviour of
soil-bentonite mix.", Vol. 25, pp. 43-49.
2. Lakshmikanth H. and Sivapulliah P.V. (2004), “Properties of Fly ash as Hydraulic Barrier”, Soil and Sediment
Contamination, Vol.13, pp. 489-504.
3. Mollamahmuto&gcaron;lu, Murat; Yilmaz, Yüksel(2001), “Potential use of fly ash and bentonite mixture as liner or
cover at waste disposal areas”, Environmental Geology;Oct2001, Vol. 40 Issue 11/12, p1316.
4. Alam J., Alam M.M. and Ahmad A. (2012), “Seepage characteristics and geotechnical properties of fly ash mixed
with bentonite”, International Journal of Scientific and Engineering Approach, Vol. 4.
5. Bello A.A.(2013),”Hydraulic conductivity of three compacted reddish brown tropical soils”, J. Civil Eng., Vol. 17, No.
5, pp. 939-948.
6. P.V.V.Satyanarayana, Harshitha.A., Sowmya Priyanka. (2013),” Utilization of red soil bentonite mixes as clay liner
materials” International Journal of Scientific & Engineering Research, Volume 4, Issue 5, May-2013 876 ISSN
2229-5518